Lake Del Valle, the Tri-Valley's big recreation lake south of Livermore, is now classified as infested with invasive golden mussels, and boaters who use it face new limits on taking their craft anywhere else in the regional park system.
The East Bay Regional Park District said the mussels had been detected in the lake in September. The Livermore Independent reported this week on how they likely got there and what officials are doing about it.
Boating rules
Any boat launched at Lake Del Valle now has to sit out a 30-day quarantine before the park district will allow it on another of its waterbodies. Boats used only at Del Valle that return still wearing an unbroken Del Valle boat band are exempt.
The district warned that other agencies around the Bay Area may set their own quarantine rules, so boaters should check before heading to another lake.
Boats without a district band must be inspected for quagga, zebra and golden mussels. The district charges $10 to inspect a motorized vessel and $5 for car-top boats and inflatables, fees it says partly cover the program. Inspections are required at Del Valle, Lake Chabot, Shadow Cliffs, Quarry Lakes and Contra Loma.
Contra Loma in Antioch had been the only district lake with golden mussels until the Del Valle find.
How they got in
District spokesperson Jen Vanya told the Independent the mussels probably came through aqueducts from the Sacramento-San Joaquin Delta. Lake Del Valle belongs to the State Water Project; the state Department of Water Resources runs it to supply local water agencies and to provide flood protection. The South Bay Aqueduct carries water to it from Bethany Reservoir, where golden mussels were found in December 2024.
Vanya said they most likely rode in with one of the regular deliveries sometime in 2025 or the first part of 2026.
